Alveolophora robusta comb. nov. from Miocene deposits of the Vitim Plateau, Russia

Abstract

The valve ultrastructure of the paramount biostratigraphic indicator species, Aulacoseira robusta Khursevich, was studied from Miocene freshwater sediments of the Vitim Plateau under light and scanning electron microscopy. Comparison between freshwater taxa of Aulacoseira Thwaites and Alveolophora Moisseeva & Nevretdinova supports the transfer of A. robusta to the genus Alveolophora. Diagnostic features of this species include robust internal pervalvar costae separating the alveolae, deep ringleiste with multiple rimoportulae and a submarginal ring of siliceous markings (short radial ridges) on the valve face.

Keywords:

• Alveolophora
• Vitim Plateau
• Miocene deposits
• fine structure
• rimoportulae
• ringleiste

Acknowledgements

This work was supported by the President's grant MK–2617.2011.5. The authors would like to thank Galina Chernyaeva for providing diatom samples, Victor Egorov for his assistance with the SEM, Patrick Kociolek for correcting the English language and two anonymous reviewers for commenting and improving the paper.